This invention relates generally to electrical devices and more particularly to devices using coils of wire arranged to develop magnetic forces, such, for example, as in solenoids or similar electrical elements. The field of endeavor to which the present invention generally relates is exemplified by patents:
Re No. 10,944 to Weston PA1 Re No. 553,675 to Haskins PA1 Re No. 928,136 to Lacy PA1 Re No. 2,082,121 to Rypinski
Each of these patents shows electrical devices having multiple coils arranged to receive electrical power and develop magnetic forces. In this respect the electromagnetic coil of the present invention is similar but the coil herein is intended for use in environments of widely varying temperatures, viz., -65.degree. F to 450.degree. F and in regions where space and weight are at a premium. Electromagnetic coils made from all copper wire have a radical change in resistance from cold to hot operating conditions, or vice versa. From 450.degree. F to -65.degree. F copper coil wattage requirements increase 260%, which is not compatible with present electronic power sources. While other types of coil wire, with less change in hot to cold resistance, are available, they have a much higher specific resistance than copper wire; therefore, coil designs embodying them adversely affect the electromagnetic performance of a coil limited to a predetermined envelope size, i.e., one composed entirely of all copper wire. The object of this invention is to provide an electromagnetic coil which will avoid the objections to coils constructed entirely of copper wire, as well as those constructed entirely of available alloys or other base metals.
It is also an object of the invention to provide an electromagnetic coil for effecting movement of a machine part such as the plunger of a valve. In many instances valves, or other electrically operated machine elements, are utilized in environments where extreme temperatures are encountered. At high altitudes, for example, temperatures as low as -65.degree. F frequently occur. In other locations, such as adjacent to gas turbine or jet engines, temperatures as high or higher than 450.degree. F are common. The provision of an electromagnetic coil which will operate without fail at such temperature extremes is a particular aim herein.
Also an object of the invention is to provide an electromagnetic coil which will operate at the previously mentioned temperature extremes without requiring excessive electrical power, insulation or package size.
Still another object of the invention is to provide an electromagnetic coil with multiple windings of wire having positive temperature coefficients of resistance, the coefficients of resistance in certain windings being different, whereby the resulting coil will be compatible with present electronic power sources.
A further object of the invention is to provide an electromagnetic coil of the character defined in the previous paragraph and in which the coil is composed of one winding of copper wire and at least one other winding of a wire with higher specific resistance/lower temperature coefficient whereby the change in hot to cold wattage will be significantly reduced with minimal impact on electromagnetic performance for a unit of predetermined size and weight.
A still further object of the invention is to provide an electromagnetic coil composed of an inner winding of copper wire and an outer winding of a wire made of copper contaminated with nickel or other suitable metal, on the order of 2%, the thicknesses of the inner and outer windings bearing a ratio between 80% to 20% and 70% to 30%.
It is an object also to provide an electromagnetic coil of the character specified in the preceding paragraph in which the outer winding is formed of wire one or two gage sizes smaller than the wire of the inner winding whereby substantially equal heat densities will exist in the windings.
Other objects and advantages will be made obvious by the following description of one embodiment of the invention selected for illustration in the accompanying drawing.